The use of BauBuche brought about not only material savings, but also height reductions and savings in construction costs and fasteners.
Material
For structural engineer Konrad Merz, the component vibration was the primary decisive factor in the design of the beams. In order to ensure the necessary stiffness, softwood glulam beams would have had to be significantly larger than the BauBuche:
| Height (with identical width = 220 mm): | |
| BauBuche | 560 mm |
| Glulam softwood | 640 mm |
In addition to the reduction in timber quantities the followings savings were achieved:
- Transport height (reduced room heights due to the material’s high load-bearing capacity)
- The low beam height of the BauBuche meant that the building envelope could be built 24 cm lower
- The reduced construction height saved a total of € 25,000 in façade costs
- Fasteners: The BauBuche beams could be laid directly on the façade columns – with softwoods, this would only have been possible with steel sheet or similar.
CO2 balance of the timber construction
In total, around 1010 m³ of timber was used for the extension to the European School. This quantity of timber creates a CO2 concentration of around 1000 tonnes in the building, which the trees extracted from the atmosphere during its growth.
A conventional, mineral construction would not only have taken twice the construction time, but would also have generated a negative CO2 balance due to the building material’s energy-intensive production: around 1000 tonnes of the greenhouse gas would have been emitted for the realisation of this building.
This clearly shows the difference: While in a timber building the CO2 is bound in the material, in the production of steel and concrete a large amount of the greenhouse gas is released.
In the case of the school expansion in Frankfurt there is a difference between the timber module solution compared to conventional massive construction of 2,000 tons of CO2. By comparison, the average footprint of Germans is about 11 tons of CO2 per year.
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Experience report by the architects – The construction of the European School was the first major timber construction project for architects Kerstin Berganski and Andreas Krawczyk
The 3D modular construction was specified by the client – why did you opt for timber room modules?
AK: The deciding factor for us was ultimately the qualitative possibilities offered by the timber construction.
We wanted to provide the users, primarily the children, with the best possible haptic qualities in the interior spaces. We also wanted the design of the building to still be something of an experience. Therefore, the visible and tactile timber surfaces in the interior spaces were really important to us. A different design where the primary construction would have needed to be permanently cladded was therefore out of the question.
In this case, the school building is only temporary, yet the modules still have a high construction quality. What arguments are still used against permanent modular solutions? This type of construction could be an affordable solution to today’s housing demands, couldn’t it?
AK: That’s a really fascinating question, and one that we’re currently very interested in. We can see a lot of potential here!
The principle of a room module without longitudinal walls that was developed during the European School project has given rise to a great deal of freedom in floorplan designs, which can of course also be applied to residential constructions. And building regulations now also include timber constructions in fire protection regulations for example. The speed and cost benefits are clear to see.
We would like to develop another project in this same direction, and not just for temporary refugee accommodation, but also as an affordable but high-quality alternative in the field of regular residential constructions. We have actually just developed a model that was discussed in detail at the Frankfurter Rundschau. However, clients still don’t seem to be very open to the idea at the moment.
What were your experiences of working with BauBuche? What stood out for you in particular?
AK: Our experiences were all very positive. We had never used BauBuche before, and were really impressed with the aesthetic quality right from the start.
Without the high load-bearing capacity of the BauBuche, which has been put to good use by the structural engineers at Merz Kley & Partner, this type of room impression would never have been possible.
Can you imagine carrying out future projects with BauBuche? And if so, what type?
AK: Of course – why not? We have since used BauBuche as flooring in a small residential project. This is a completely new and really pleasant surface that one doesn’t immediately expect to see on a floor, but that develops a really unique quality there.
We’ll have to wait and see what else might be in store. We’re open to anything. This development is still right at the early stages, which is a very exciting prospect for us.
Field report from Frankfurt – The city of Frankfurt had to meet diverse requirements with its expansion of the European School
The department manager and architect at Frankfurt’s construction authority, construction director Harald Heußer, is convinced by the advantages of the modular design:
Mr Heußer, what do you consider to be the most important advantages?
The advantages lie primarily in the flexibility of the design and the extremely short realisation period of just 7 months, i.e., almost half the time required for solid constructions. Yet the decisive factor turned out to be the architectural quality of the interior. Despite their modularity, the buildings do not have that provisional feel which is so often associated with temporary structures. The design has met with high levels of approval from staff and students alike.
To what extent has Frankfurt benefited from this approach to construction?
When a school needs to be renovated, the pupils inevitably have to be relocated. In the past, this has often led to heated discussions with parents who don’t want their children to be taught in container constructions for years on end. But now that we can offer timber modular structures this is no longer a problem. The buildings with a timber modular design are accepted as adequate school structures. The high-quality wall surfaces made of white fir/3S boards or glazed OSB boards are also undoubtedly key to the acceptance of these wooden modular constructions.
Could the timber modular design offer a solution for other urban challenges?
This design approach is ideal in particular for construction tasks which need to combine speed with high quality and architecturally pleasing interiors. In other words, buildings to which you would be happy to send your children to spend longer periods of time during an important phase of their lives.
The applications are not restricted to school relocations – the timber modular concept also presents an interesting approach for the construction of nurseries and changing rooms at sports facilities.
Are projects of this type already being planned?
We are currently in the process of developing a standardised timber module which will offer the same flexibility and compatibility as the steel containers which have been successfully launched on the market. Our standard type is to be produced by various providers based on our geometric and construction physics specifications. The “Frankfurt” modular design should be able to be composed of a standard module for the classroom, a corridor module or a sanitary module etc. Using these elements smaller or larger schools ranging from one to three storeys can be developed to suit requirements. This construction type is intended for temporary school buildings with a life time of 4 to 8 years. The building will comply with the requirements of the Energy Saving Ordinance (ENEV) and, amongst other things, all the parameters of modern structural sound insulation. Given their exceptional architectural quality, these timber modular structures are not regarded as “impositions” on the urban landscape, but are rather seen as a high-quality addition to the environment.
A number of major projects are in the planning process in Frankfurt, some of which will far exceed the scale of the European School. In the west of Frankfurt a grammar school with 6 classes in each year, a sports hall and canteen for almost 2000 pupils is to be realised using a timber modular design. In the district of Riedberg a temporary timber modular structure is currently being built. This will act as a “starter school” for children in this new Frankfurt district whilst the planned comprehensive school is being built on the same site.
After around 2 years, the school will be disassembled and set up again at another site.
No doubt the green light will be given for further projects in the near future.
